1. Field of the Present Invention
The present invention relates generally to lubrication systems for bearing supporting the shaft in the turbine engine, and more particularly to seals which can be selectively engaged between the parts between which lubricant flow is to be controlled.
2. Description of the Prior Art
It is well known that turbine shafts typically rotate at high speeds within bearings supported in a turbine housing. As a result, bearings must be lubricated to prevent overheating and failure due to friction in the bearings. A previously known means for lubricating the bearing comprises partial or complete immersion of the rotating shaft in an oil supply reservoir. In order to prevent leakage of the lubricant along the shaft away from the oil reservoir, seal means have been disposed between rotating and stationary elements to prevent lubricant loss. Previously known seal structures between rotating and stationary parts often comprise dynamic seals in which carbon elements are held in contact with a metallic ring or face. While such seals function adequately during periods of operation, as rotary motion of one part relative to the other increases the sealing ability of the seals, prolonged storage or periods of non-operation enables seepage of the lubricant past the seal elements to occur, especially if the seals have become worn.
As a result, previously known dynamic seals require inspection and servicing at frequent intervals so that the seals continue to function adequately. Moreover, if the turbine is to be stored for an extended period of time, it is necessary as a practical matter to partially disassemble the turbine for the installation of positive static seals which prevent lubricant leakage during storage. Moreover, previously known positive seals are often constructed so that when the engine is again operated, the seals are destroyed and consumed by the engine operation. Thus, even the positive seals must be repeatedly replaced if the turbine engine is repeatedly stored and operated.